As described in my copending application Ser. No. 08/255,778 filed 8 June 1994 (now U.S. Pat. No. 5,435,163 issued 24 July 1995) it is known to bulge-form a tubular workpiece by means of an apparatus that has a stationary base, a die fixed on the base and formed with a cavity having an inner surface and axially oppositely open ends so that a tubular workpiece can be held in the cavity with ends of the workpiece exposed at the ends of the cavity, and a pair of pistons fittable with the workpiece ends. Respective actuators can displace the pistons toward each other and against the ends of the workpiece in the cavity. A hydraulic liquid is fed at high pressure through one of the pistons to an interior of the workpiece in the cavity to deform the workpiece. Respective first guides support the pistons on the base for vertical movement thereon, respective second guides support the pistons on the base for horizontal movement thereon, and respective third guides support the pistons on the base for pivotal movement about respective centers.
With such an arrangement (See also Werkstatt und Betrieb 122 [1989]9 p. 767.) it is standard for the actuators and a lower die half to be mounted on a horizontal plate, with the upper die half being pushed down onto the lower half to form the die cavity around the tubular workpiece, whereupon the actuators advance the pistons to allow the workpiece interior to be pressurized. The pressure is so great, often in excess of 1000 kp/mm.sup.2, that the tubular workpiece is bulged outward to conform to the interior of the die, producing a finished product that is cold-formed to high tolerances.
In an automated production line a robot is used to load and unload the die. Thus once the workpiece is fully formed the upper die half is raised and the two pistons are retracted so that the robot can pick out the finished part. Then the robot fetches another workpiece and places it in the lower die cavity, whereupon the cycle can be repeated. Such a procedure is relatively time consuming.
Even though in some systems (See U.S. Pat. Nos. 2,252,626 and 3,452,577.) it is known to orient the press parts to somewhat facilitate loading and unloading operations, these known systems remain fairly clumsy and inefficient. They are not readily adaptable to a high-pressure bulge-forming press.